70 NAIADACEAE 



Montane region at 5000 to 7000 feet alt. : Bear Valley, San Bernardino Mts., 

 Parish; Sierra Nevada; i\It. Shasta; northward to British Columbia and east 



to the Atlantic. Europe, Asia. 



Kefs.— POTAMOGETON N.A.TAKS L. Sp. PI. 126 (1753); Wats. Bot. Cal. 2: 195 (1880); 

 Morong, Mem. Torr. Club, 3=: 13, pi. 25 (1893). 



2. P. epihydrus Raf. Stems slender (1/2 line broad), compressed, mostly 

 simple, 1 to 2 feet long; floating leaves narrowly oblong, 1% to 2 inches long, 

 gradually narrowed into petioles about 1/0 as long; submerged leaves thin, 

 grass-like, 2 to 3 inches long, 2 to 3 lines wide, the petiole-like base very short ; 

 spikes dense, % inch long, on pediuicles 11/4 f IV2 inches long ; nutlet flatfish, 

 3-keeled, the seed impressed ou the sides. 



Yosemite Valley {Bolander 6393), north to British Columbia and east to the 



Atlantic States. 



Refs. — PoTAMOGETON EPIHYDRUS Raf. Med. Repos. 2d ser. 5: 3.54 (1808). P. nuttallii C. & 

 S. Linnaea, 2: 226 (1827). P. daytoni Tuckerm. Am. Jour. Sci. 1st ser. 45: 38 (1843) ; Wats. 

 Bot. Cal. 2: 195 (1880). 



3. p. dimorphus Raf. Stems simple, 114 feet long; floating leaves in 2 or 

 3 opposite pairs, oblong, tapering to each end, impressed beneath with 7 to 9 

 nerves, 3 to 4 lines wide and 7 to 10 lines long, passing rather definitely at base 

 into the somewhat shorter (or sometimes longer) petiole; submerged leaves 

 1/4 to % line wide, 1 or 2 inches long, acute at tip but not setaceous, stipules 



1 to 5 lines long, adnate for about 1/. their length; flowers in a few-flowered 

 head (or the emersed in a very short spike), the peduncles 1 to 3 lines long, 

 shorter than the submersed spike ; nutlet less than 1 line long, keeled on the 

 back, the keel winged and sometimes dentirulate; emljryo coiled li-j times; 

 pericarp very thin and fleshless. revealing clearly the coiled embryo, the whole 

 suggestive of a snail shell. 



Lake Surprise, San Jacinto ilts., alt. 9000 feet, Hall 2490; near Visalia 

 ace, Bot. Death Valley; irrigating ditches at Turloek. Missouri to Virginia 



and Nova Scotia. 



Refs. — PoTAMOOETON DIMORPHUS Raf. Am. Mo. Mag. 1: 358 (1817). P. spirillus Tuckerm. 

 Am. Journ. Sei. 2d ser. 6: 228 (1848); Morong, Mem. Torr. Club, 3=: 49, pi. 56 (1893). 



P. HYBRiDUS Michx. Very similar to P. dimorphus but peduncles eciualing 

 or longer than submersed spike, frequently recurved ; keels toothed. — Credited 

 to California by Taylor (N. Am. PI. 17^: 17). 



4. P, alpinus Balbis, Alpine Pondweed. Whole plant of a reddish tinge; 

 stems simple, 1 or 2 feet long; floating leaves narrowly oblong, tapering at 

 both ends, 2 to 4 inches long, % to % inch wide, submerged leaves 2 to 7 inches 

 long, 1/4 to 1/2 inch wide, all sessile or narrowed to a short petiole ; stipules 

 broad, i/o to I14 inches long; spikes % to 1\'$, inches long, on peduncles about 



2 inches long; nutlet with a distinct pit on each side. 



Ponds in the high mountains : Sierra Nevada, North Fork of Kings Kiver, 

 7000 feet alt.. Hall & Chandler; Silver Valley, Alpine Co., 7200 feet alt.. 

 Brewer 1978 ; north to Alaska and east to Florida and Labrador. Europe, 

 Asia. 



Refs. — POTAMOGETON ALPINUS Balbis, Misc. 13 (1804); Morong, Mem. Torr. Club, 3': 19, 

 pi. 30 (1893). P. rufescens Schrader; Chamisso, Adnot. Fl. Berol. 5 (1815) ; Wats. Bot. Cal. 

 2: 195 (1880). 



5. P. amerlcanus C. & S. Stems terete, much branched, 3 to 6 feet long; 

 floating leaves coriaceous, elliptical, 2 to 4 inches long, 14 to IY2 inches wide, 

 the petiole often longer than the blade, submerged leaves very thin, lanceolate, 



